Rotary drill bits are frequently used to drill oil and gas wells, geothermal wells and water wells. Rotary drill bits may be generally classified as rotary cone or roller cone drill bits and fixed cutter drilling equipment or drag bits. Fixed cutter drill bits or drag bits are often formed with a bit body having cutting elements or inserts disposed at select locations of exterior portions of the bit body. Fluid flow passageways are typically formed in the bit body to allow communication of drilling fluids from associated surface drilling equipment through a drill string or drill pipe attached to the bit body.
Fixed cutter drill bits generally include a metal shank operable for engagement with a drill string or drill pipe. Various types of steel alloys may be used to form a metal shank. A bit head may be attached to an associated shank to form a resulting bit body.
For some applications a bit head may be formed from various types of steel alloys satisfactory for use in drilling a wellbore through a downhole formation. The resulting bit body may sometimes be described as a “steel bit body.” For other applications, a bit head may be formed by molding hard, refractory materials with a metal blank. A steel shank may be attached to the metal blank. The resulting bit body may be described as a “matrix bit body.”Fixed cutter drill bits or drag bits formed with matrix bit bodies may sometimes be referred to as “matrix drill bits.”
Various techniques have previously been used to form molds associated with fabrication of matrix bit bodies and/or steel bit bodies for fixed cutter drill bits. For example numerically controlled machines and/or manual machining processes have been used to fabricate molds from various types of raw material blanks. For example, graphite based materials in the form of solid, cylindrical blanks have been machined to form a mold cavity with dimensions and configurations that represent a negative image of a bit head for an associated matrix drill bit.
Matrix drill bits are often formed by placing loose infiltration material or matrix material (sometimes referred to as “matrix powder”) into a mold and infiltrating the matrix material with a binder such as a copper alloy. Other metallic alloys may also be used as a binder. Infiltration materials may include various refractory materials. A preformed metal blank or bit blank may also be placed in the mold to provide reinforcement for a resulting matrix bit head. The mold may be formed by milling a block of material such as graphite to define a mold cavity with features corresponding generally with desired exterior features of a resulting matrix drill bit.
Various features of a resulting matrix drill bit such as blades, cutter pockets, and/or fluid flow passageways may be provided by shaping the mold cavity and/or by positioning temporary displacement material within interior portions of the mold cavity. An associated metal shank may be attached to the bit blank after the matrix bit head has been removed from the mold. The metal shank may be used to attach of the resulting matrix drill bit with a drill string.
A wide variety of molds has been used to form matrix bit bodies and associated matrix drill bits. U.S. Pat. No. 5,373,907 entitled “Method And Apparatus For Manufacturing And Inspecting The Quality Of A Matrix Body Drill Bit” shows some details concerning conventional mold assemblies and matrix bit bodies.
A wide variety of molds and castings produced by such molds have been used to form steel bit bodies and associated fixed cutter drill bits.
More recently, three dimensional (3D) printing equipment and techniques have been used in combination with three dimensional (3D) design data associated with a wide variety of well drilling equipment and well completion equipment to form molds for producing various components associated with such equipment. For some applications refractory materials, infiltration materials and/or matrix materials, typically in a powder form, may be placed in such molds. For other applications molten steel alloys or other molten metal alloys may be poured into such molds.
A wide variety of equipment and procedures have been developed to form models, molds and prototypes using automated layering devices. U.S. Pat. No. 6,353,771 entitled “Rapid Manufacturing Of Molds For Forming Drill Bits” provides examples of such equipment and procedures.
Various techniques and procedures have also been developed to use three dimensional (3D) printers to form models, molds and prototypes using 3D design data. See, for example, information available at the websites of Z Corporation (www.zcorp.com); Prometal, a division of The Ex One Company (www.prometal.com); EOS GmbH (www.eos.info); and 3D Systems, Inc. (www.3dsystems.com); and Stratasys, Inc. (www.stratasys.com and www.dimensionprinting.com).
U.S. Pat. No. 5,204,055 entitled 3-Dimensional Printing Techniques and Related Patents discusses various techniques such as ink jet printing to deposit thin layers of material and inject binder material to bond each layer of powder material. Such techniques have been used to “print” molds satisfactory for metal casting of relatively complex configurations. U.S. Pat. No. 7,070,734 entitled “Blended Powder Solid-Supersolidus Liquid Phase Sentencing” and U.S. Pat. No. 7,087,109 entitled “Three Dimensional Printing Material System and Method” also disclose various features of 3D printing equipment which may be used with 3D design data. Another technique for 3D printing, known as Selective Laser Sintering (SLS). Details of one such application of this technique and related equipment are disclosed in U.S. Pat. No. 5,147,587 A.
It is in general important to control both heating and cooling of matrix materials or cooling of molten metal alloys to provide optimum fracture resistance (toughness), optimum tensile strength and/or optimum erosion, abrasion and/or wear resistance of resulting components, and to avoid molding or casting defects.
For example, by using three dimensional (3D) printing equipment and techniques, three dimensional (3D) computer aided design (CAD) data associated with fixed cutter drill bits may be used to produce respective molds each having a mold cavity that is essentially a “negative image” of various portions of each fixed cutter drill bit. Such molds may be used to form a matrix bit head or a steel bit head for a respective fixed cutter drill bit. U.S. Pat. No. 6,296,069 entitled “Bladed Drill Bit with Centrally Distributed Diamond Cutters” and U.S. Pat. No. 6,302,224 entitled “Drag-Bit Drilling with Multiaxial Tooth Inserts” show various examples of blades and/or cutting elements which may be used with a matrix bit body. Various components of other well tools may also be molded as matrix bodies.
In this regard, U.S. Patent Application Publication No. 2007/0277651 A1, to Calnan et al., entitled “Molds and Methods of Forming Molds Associated With Manufacture of Rotary Drill Bits and Other Downhole Tools”, proposes using 3D printing equipment in combination with 3D design data to form respective portions of a mold from materials having different thermal conductivity and/or electrical conductivity characteristics.
In particular, Calnan et al. contemplate that providing high thermal conductivity proximate a first end or bottom portion of a mold may improve heat transfer during heating and cooling of materials disposed within the mold. Thermal conductivity may be relatively low proximate a second end or top portion of the mold, so that that portion of the mold will function as an insulator for better control of heating and/or cooling of materials disposed within the mold. Specifically, Calnan et al. envision that, for some applications, two or more layers of sand or other materials with different heat transfer characteristics may be used to form molds. It is to be understood that the two or more layers in question are two or more of the same horizontal layers of mold material which are sequentially deposited and built up in the 3D printing process by which the mold is formed.
Calnan et al. further propose to form a mold having variations in electrical conductivity to accommodate varying heating and/or cooling rates of materials disposed within the mold. For example, one or more portions of the mold may be formed from materials having electrical conductivity characteristics compatible with an associated microwave heating system or an induction heating system. As a result, such portions of the mold may be heated to a higher temperature and/or heated at a higher rate than other portions of the mold which do not have such electrical conductivity characteristics.
Furthermore, Calnan et al. contemplate placing degassing channels within a mold to allow degassing or off gassing of materials disposed within the mold, as well as providing fluid flow channels on interior and/or exterior portions of a mold to heat and/or cool materials disposed within the mold. Various types of liquids and/or gases may be circulated through such fluid flow channels.